DataAccessLayer.DataBase.GetAccountByLogin C# (CSharp) Method

        public Account GetAccountByLogin(string username, bool checkExisting)
        {
            string queryString =
                "SELECT [dbo].accounts.accountid, login, password, mail, city, country, [dbo].accounts.name, [dbo].Roles.Name, [dbo].accounts.photo, [dbo].accounts.mimetype " +
                "FROM [dbo].accounts, [dbo].UsersRoles, [dbo].Roles " +
                "WHERE (login = @login) AND ([dbo].accounts.accountid = [dbo].UsersRoles.AccountId) AND ([dbo].UsersRoles.RoleId = [dbo].Roles.RoleId);";

            using (SqlConnection connection = new SqlConnection(_connectionString))
            {
                var command = new SqlCommand(queryString, connection);

                command.Parameters.AddWithValue("login", username);

                connection.Open();
                var reader = command.ExecuteReader();

                if (reader == null)
                {
                    return null;
                }

                while (reader.Read())
                {
                    if (!checkExisting)
                    {
                        return new Account()
                        {
                            Id = (Guid)reader[0],
                            Login = (string)reader[1],
                            Password = (string)reader[2],
                            Email = (string)reader[3],
                            City = (string)reader[4],
                            Country = (string)reader[5],
                            Name = (string)reader[6],
                            Role = ((string)reader[7]).Split(','),
                            Avatar = (byte[])reader[8],
                            MimeType = (string)reader[9]
                        };
                    }
                    else
                    {
                        return new Account()
                        {
                            Id = (Guid)reader[0],
                            Password = (string)reader[2],
                            Role = ((string)reader[7]).Split(',')
                        };
                    }

                }

                return null;
            }
        }